Ms. hugger after taking the egee 102 class, added more insulation to her attic (500 sq. ft) at a cost of 1144 dollars. after the addition, she noticed that her heat loss from the entire house went down from 42 million btus to 28 million btus. she heats her home with natural gas at a cost of $8.94 per mcf. what is her pay back period?

payback period is 9.4785 ≅ 9.5 years  

Explanation:

BTU stands for British thermal units and MCF stands for the volume of 1,000 cubic feet.

We know that one thousand cubic feet (Mcf) of natural gas equals 1.037 million Btu.

Difference between heat loss before and after installation = (42-28) millions BTU =  14 millions BTU

14 million BTU is equivalent to --

1.037 million BTU = 1 MCF

1 million BTU = (1/1.037) MCF

14 million BTU = (1/1.037) x 14 MCF = 13.5004 MCF

Cost of 13.5004 MCF = = $8.94 x 13.5004  = $120.6935

Pay back period = (1144/120.6935) = 9.4785

Therefore, her payback period is 9.4785 ≅ 9.5 years

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